Lightly heat both sides of tortillas – either via microwave or on stovetop. Heat enchilada sauce, black beans and refried beans on low heat in seperate pans. Dip tortillas in enchilada sauce, both sides. Lay in glass pan. Top with beans, and a handful of avocado, salsa, cheese, tomatoes and onion. Layer with tortillas, followed by beans and veggies and another layer of tortillas. Pour remaining sauce over top of casserole. Top with grated cheese. Add green onions on top for aesthetics. Bake 30 minutes at 350 degrees.